If you're a farmer who generously applies certain pesticides to your crops - losing your sense of smell has just taken on a whole new meaning. It could foreshadow health problems down the road.

Decades of research - recently published - has found a significant link between a chronic loss of smell (olfactory impairment or "OI") among American farmers, and their high exposure to certain chemicals they applied to their fields. Far from being a minor ailment, "OI" has long been identified as one of the earliest and most important symptoms of several neurological diseases, including Parkinson's and Alzheimer's.
by Larry Powell
The human "olfactory" system governs 
our sense of smell. Image - public domain.

Beginning in the '90s, a team of US scientists surveyed more than 11 thousand farmers from Iowa and North Carolina. They were asked about their experiences with farm chemicals during their lifetimes.

In 2015, there was a follow-up survey. Almost 12 hundred (10.6%) reported they had either lost, or significantly lost, their sense of smell. And those who reported incidents of unusually high exposure to pesticides during that time, were almost 50% more likely to report the symptom than those who did not. These mishaps are identified in the research as "High Pesticide Exposure Events" or "HPEEs." In them, the farmers either accidentally swallowed, inhaled or spilled the pesticides on their skin.

And those who did not wash thoroughly with soap and water within four hours of exposure, stood a greater chance of developing "OI". In other words, those who washed quickly likely helped reduce their harmful effects.

The pesticides named in the analysis include DDT, an insecticide no longer used in North America. The researchers believe the older farmers reporting symptoms were exposed to it, even before it was banned back in the '60s. DDT and the other insecticide named, lindane, are persistent and can still be found in food, the environment and even human tissue. They belong to a family known as organochlorines. Even before this latest research,  organochlorines had been associated with both Parkinson's and dementia.

Four other pesticides are also implicated. They include 2,4-D, a popular weedkiller still in use. 

Honglei Chen, MD, PhD, professor
of epidemiology, Michigan State U.
In an e-mail to "Planet in Peril," the lead author of the study, Honglei Chen (l.) further explains, "Poor sense of smell predicts higher mortality and risk for neurodegenerative diseases after accounting for other risk factors such as age, sex, smoking and health status."

The report concludes: "To the best of our knowledge, our study provides the first empirical evidence that acute high exposure to pesticides may lead to poor sense of smell among older farmers."

A ground sprayer in Canada, where farming methods, including
heavy inputs of chemical pesticides, closely 
resemble those in the US. A PinP photo.

The research was conducted by nine US experts. They represented groups including the National Institutes of Health and the National Cancer Institute. Their report was published in January in the journal, "Environmental Health Perspectives."  It calls for more studies to further explore the issue.

"OI" also affects us in other ways few might imagine. 

Even certain accidents can be attributed to a loss of smell. For example, if you can't smell properly, you may be unable to detect stove fires due to burning pots or pans, gas leaks, food gone bad or toxic substances in time to avoid an accident. Even weight gain has been shown to be highest among those with "OI." And among women age 45 to 60 years who were tested, an ability to smell well "significantly improved" their tension, depression and confusion levels. And pesticides may even be responsible for a loss of smell among honeybees, disrupting their ability to find pollen and nectar.  


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